Apache virtual() failures with session module

Description

This is taken from the note in docs: https://www.php.net/manual/en/function.virtual.php#124597

Starting with 7.2 various session related things were changed and it seems part of it is conflicting with virtual(). Calling it you may receive a "PHP Warning: virtual(): Headers already sent. You cannot change the session module's ini settings at this time in ..." although no header was set and virtual() should simply provide static content from a file.

It took half a day to find out that some main session.configuration.php settings (e.g. save_handler, serialize_handler, or save_path) in the Apache config (all levels) are causing this. It seems the settings are regarded as likely to change headers but virtual() is already beyond sending them. Unfortunately the warning is then not only logged to error_log but also part of the content virtual() sends to the client which screws it up - the format of the content like binary image data is no more correct.

If you do not need php's session management you can remove all session.* settings in your apache configuration to avoid the warning. Otherwise a workaround is to switch off E_WARNING before calling virtual().

<?php
$filename = '/data/image.jpg';
$level = error_reporting();
error_reporting($level & ~E_WARNING); 
virtual($filename);
error_reporting($level);
?>

This will be most likely related sharing of globals and will require some restoring of parent globals like. It needs more checking if it's just for SG(headers_sent) or some session globals as well. In general, there are likely more issue with re-using globals in this way so this might probably need some deeper review. I guess it would be still worth to fix the session specific issues and do a bit more testing to see if more generic approach makes sense.

PHP Version

PHP 8.3+

Operating System

No response

Reproduce virtual() with the session.* settings described in an Apache configuration, then inspect the virtual() and session-module paths around SG(headers_sent) and shared globals. Confirm whether session-specific state is being reused or restored incorrectly. Done means the warning is no longer injected into virtual() output and binary content remains intact, with the relevant behavior tested.